I get a female one in my SS game. My sister wants a female Eevee also in her SS (note: my sister didn't reach Goldenrod, so she can't get one by herself). I breed my Eevee, but it ended up with a male Eevee hatched from the egg (the female Eevee ratio is 12,5%).
No, the Eevee you get from Bill will always have the same old 87.5% chance of being male.
And breeding does not affect the gender either.